Dimethylformamide Impurities as Propylene Polymerization Inhibitor.

This research study examined how the use of dimethylformamide (DMF) as an inhibitor affects the propylene polymerization process when using a Ziegler-Natta catalyst. Several experiments were carried out using TiCl4/MgCl2 as a catalyst, aluminum trialkyl as a cocatalyst, and different amounts of DMF. Then, we analyzed how DMF influences other aspects of the process, such as catalyst activity, molecular weight, and the number of branches in the polymer chains obtained, using experimental and computational methods. The results revealed that as the DMF/Ti ratio increases, the catalyst activity decreases. From a concentration of 5.11 ppm of DMF, a decrease in catalyst activity was observed, ranging from 45 TM/Kg to 44 TM/Kg. When the DMF concentration was increased to 40.23 ppm, the catalyst activity decreased to 43 TM/Kg, and with 75.32 ppm, it dropped even further to 39 TM/Kg. The highest concentration of DMF evaluated, 89.92 ppm, resulted in a catalyst productivity of 36.5 TM/Kg and lost productivity of 22%. In addition, significant changes in the polymer's melt flow index (MFI) were noted as the DMF concentration increased. When 89.92 ppm of DMF was added, the MFI loss was 75%, indicating a higher flowability of the polymer. In this study, it was found that dimethylformamide (DMF) exhibits a strong affinity for the titanium center of a Ziegler-Natta (ZN) catalyst, with an adsorption energy (Ead) of approximately -46.157 kcal/mol, indicating a robust interaction. This affinity is significantly higher compared to propylene, which has an Ead of approximately -5.2 kcal/mol. The study also revealed that the energy gap between the highest occupied molecular orbital (HOMO) of DMF and the lowest unoccupied molecular orbital (SOMO) of the Ziegler-Natta (ZN) catalyst is energetically favorable, with a value of approximately 0.311 eV.

Thermodynamic analysis and preferential solvation of gatifloxacin in DMF + methanol cosolvent mixtures / Análisis termodinâmico y solvatación preferencial de gatifloxacina en mezclas cosolventes DMF + metanol

SUMMARY This paper presents the thermodynamic analysis of solubility of gatifloxacin in the N,N-Dimethylformamide (DMF) + methanol (MeOH) cosolvent system at 10 temperatures. From the solubility data, the thermodynamic functions of solution, mixing, and transfers are calculated and analyzed using the Perlovich graphical method. On the other hand, an enthalpy-entropy compensation analysis is performed and the preferential solvation parameters are calculated using the inverse Kirkwood-Buff integral (IKBI) method. The result of the performed calculations indicates that the gatifloxacin solution process is endothermic with entropic favor, where the addition of DMF has a positive cosolvent effect in all cases. Regarding preferential solvation, the results are not entirely conclusive, since in all cases the values of the preferential solvation parameter are less than 0.01, so that, negligible preferential solvation takes place.

RESUMEN Este artículo presenta el análisis termodinâmico de la solubilidad de gatifloxacina en el sistema cosolvente de A,A-Dimetilformamida (DMF) + metanol (MeOH) a 10 temperaturas. A partir de los datos de solubilidad se calculan las funciones termodinámicas de solución, mezcla y transferencia. Para el análisis además se utiliza el método gráfico Perlovich. Por otro lado, se realiza un análisis de compensación entalpía-entropía y se calculan los parámetros de solvatación preferencial utilizando el método de las integrales inversas de Kirkwood-BufF (IIKB). Los resultados del análisis termodinámico indican que el proceso de solución de gatifloxacina es endotérmica con favorecimiento entrópico, donde la adición de DMF tiene un efecto cosolvente positivo en todos los casos. En cuanto a la solvatación preferencial, los resultados no son del todo concluyentes, debido a que en todos los casos los valores del parámetro de solvatación preferencial son menores a 0,01 indicando una solvatación insignificante.

The Effect of N-N-Dimethylformamide on the Membrane Characteristics of Canine Spermatozoa After Cryopreservation, and its Relationship With Post-Thaw Motility.

Some studies have demonstrated that glycerol is superior to amides in preserving sperm motion characteristics of canine sperm; however, little is known about the effect of these cryoprotectants on the membrane characteristics of canine spermatozoa after freezing/thawing. In this study, the effects of using either N-N-dimethylformamide (DMF) or glycerol (GLY) on the integrity and function of the canine sperm, after cryopreservation were determined. We hypothesized that the use of a multiparametric approach for assessing the effect of DMF on the membranes of canine sperm would explain the lower values reported for post-thaw motility. Ejaculates from 12 dogs were collected, split into 2 groups, and frozen using a tris-fructose-citrate-egg yolk-based extender containing either 7% (v/v) GLY or 7% (v/v) DMF. Frozen straws (n = 120) were thawed and analyzed for subjectively-assessed sperm progressive motility, normal morphology, plasma membrane integrity, plasma membrane function (HOST+), acrosome membrane integrity, high mitochondrial membrane potential, and simultaneous assessment of sperm membrane integrity and function by a triple-staining fluorescent procedure. Overall, sperm motility and membrane intactness/function were higher when GLY was used as a cryoprotectant, as compared to DMF (P < .05). A model to explain the variation in progressive motility using the values obtained from the sperm integrity and function parameters was designed. The percent HOST+ sperm and high mitochondrial membrane potential sperm were mostly associated with the changes observed in the progressive motility (r2 = 0.84; P = .043) when either GLY or DMF were used as cryoprotectants. These results may explain the overall reduced sperm quality observed after cryopreservation, as a reflection of sublethal damage sustained by the sperm membranes.

Development, Fabrication, and Characterization of Composite Polycaprolactone Membranes Reinforced with TiO2 Nanoparticles.

This paper focuses on developing, fabricating, and characterizing composite polycaprolactone (PCL) membranes reinforced with titanium dioxide nanoparticles (NPs) elaborated by using two solvents; acetic acid and a mixture of chloroform and N,N-dimethylformamide (DMF). The resulting physical, chemical, and mechanical properties of the composite materials are studied by using experimental characterization techniques such as scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-Ray diffraction (XRD), Fourier-transform infrared (FTIR) analysis, contact angle (CA), uniaxial and biaxial tensile tests, and surface roughness measurements. Experimental results show that the composite material synthesized by sol-gel and chloroform-DMF has a better performance than the one obtained by using acetic acid as a solvent.

Identificación de biomarcadores saturados en un carbón bituminoso tratado con ácido y un solvente no convencional / Identification of biomarkers in a bituminous coal treated with acid and an unconventional solvent / Identificação de biomarcadores saturados em carvão betuminoso tratado com ácido e solvente não convencional

Resumen Este artículo describe los biomarcadores saturados (n־alcanos, hopanos y esteranos) identificados en los extractos obtenidos de un carbón bituminoso, tratado con ácido y un solvente no convencional. Los extractos de carbones bituminosos venezolanos se obtuvieron a través de cloroformo (solvente convencional) y N,N־dimetilformamida ־DMF־ como solvente de alto poder extractivo, con y sin tratamiento ácido previo, con el fin de evaluar el rendimiento y distribución de biomarcadores característicos. El rendimiento de extracción con DMF alcanzó 44% p/p, mientras que con CHCl3, este valor no superó el 2% p/p. La desmineralización previa con HCl incrementó el rendimiento de extracción sin afectar la distribución de los biomarcadores, salvo en la relación de hidrocarburos ligeros respecto a los pesados. Se propone DMF como solvente de elección para obtener información geoquímica en carbones meteorizados.

Abstract This article describes saturated biomarkers (n־alkanes, hopanes and steranes) identified in the extracts obtained from a bituminous coal treated with acid and an unconventional solvent. Extracts of Venezuelan bituminous coals were obtained through chloroform (conventional solvent) and N,N־ dimethylformamide ־DMF־ as high extractive solvent, with and without previous acid treatment, to evaluate the performance and distribution of characteristic biomarkers. The extraction yield with DMF reached 44% w/w, while with CHCl3, this value did not exceed 2% w/w. Previous demineralization with HCl increased the extraction yield without affecting the distribution of the biomarkers, except in the ratio of light hydrocarbons to the heavy ones. DMF, therefore, is proposed as the solvent of choice to obtain geochemical information on weathered carbons.

Resumo Este artigo de pesquisa descreve os biomarcadores saturados identificados (n־alcanos, hopanos y esteranos) em extratos obtidos a partir de carvão betuminoso, tratado com ácido e um solvente não convencional. Extratos de carvão betuminoso venezuelano foram obtidos utilizando־se clorofórmio (solvente convencional) e N,N־ dimetilformamida ־DMF־ como solvente extrativo elevado, com e sem tratamento ácido prévio, com o objectivo de avaliar o rendimento e distribuição de biomarcadores característicos. O rendimento de extração com DMF atingiu 44% p/p; com CHCl3 o valor não excedeu 2% p/p. A desmineralização prévia com HCl aumentou o rendimento da extração sem afetar a distribuição dos biomarcadores, exceto na proporção de hidrocarbonetos leves e pesados. DMF é proposto como o solvente de eleição para obter informações geoquímicas sobre os carvões intemperizados.

Vanadium: History, chemistry, interactions with α-amino acids and potential therapeutic applications.

In the last 30 years, since the discovery that vanadium is a cofactor found in certain enzymes of tunicates and possibly in mammals, different vanadium-based drugs have been developed targeting to treat different pathologies. So far, the in vitro studies of the insulin mimetic, antitumor and antiparasitic activity of certain compounds of vanadium have resulted in a great boom of its inorganic and bioinorganic chemistry. Chemical speciation studies of vanadium with amino acids under controlled conditions or, even in blood plasma, are essential for the understanding of the biotransformation of e.g. vanadium antidiabetic complexes at the physiological level, providing clues of their mechanism of action. The present article carries out a bibliographical research emphaticizing the chemical speciation of the vanadium with different amino acids and reviewing also some other important aspects such as its chemistry and therapeutical applications of several vanadium complexes.

Single-step solubilization of milk samples with N,N-dimethylformamide for inductively coupled plasma-mass spectrometry analysis and classification based on their elemental composition.

A single-step procedure for trace elements analysis of milk samples is presented. Solubilization with small amounts of dymethylformamide (DMF) was assayed prior to inductively coupled plasma mass spectrometry (ICPMS) detection with a high efficiency sample introduction system. All main instrumental conditions were optimized in order to readily introduce the samples without matrix elimination. In order to assess and mitigate matrix effects in the determination of As, Cd, Co, Cu, Eu, Ga, Gd, Ge, Mn, Mo, Nb, Nd, Ni, Pb, Pr, Rb, Sm, S, Sr, Ta, Tb, V, Zn, and Zr, matrix matching calibration with (103)Rh as internal standard (IS) was performed. The obtained limits of detection were between 0.68 (Tb) and 30 (Zn) µg L(-1). For accuracy verification, certified Skim milk powder reference material (BCR 063R) was employed. The developed method was applied to trace elements analysis of commercially available milks. Principal components analysis was used to correlate the content of trace metals with the kind of milk, obtaining a classification according to adults, baby or baby fortified milks. The outcomes highlight a simple and fast approach that could be trustworthy for routine analysis, quality control and traceability of milks.

Transmission FTIR derivative spectroscopy for estimation of furosemide in raw material and tablet dosage form.

A Fourier transform infrared derivative spectroscopy (FTIR-DS) method has been developed for determining furosemide (FUR) in pharmaceutical solid dosage form. The method involves the extraction of FUR from tablets with N,N-dimethylformamide by sonication and direct measurement in liquid phase mode using a reduced path length cell. In general, the spectra were measured in transmission mode and the equipment was configured to collect a spectrum at 4 cm(-1) resolution and a 13 s collection time (10 scans co-added). The spectra were collected between 1400 cm(-1) and 450 cm(-1). Derivative spectroscopy was used for data processing and quantitative measurement using the peak area of the second order spectrum of the major spectral band found at 1165 cm(-1) (SO2 stretching of FUR) with baseline correction. The method fulfilled most validation requirements in the 2 mg/mL and 20 mg/mL range, with a 0.9998 coefficient of determination obtained by simple calibration model, and a general coefficient of variation <2%. The mean recovery for the proposed assay method resulted within the (100±3)% over the 80%-120% range of the target concentration. The results agree with a pharmacopoeial method and, therefore, could be considered interchangeable.

Comparação de métodos diretos de extração e quantificação dos teores de clorofilas em folhas do capim-Tifton 85 / Comparison of direct methods of extraction and chlorophyll contents quantification in leaves of Tifton 85 bermudagrass

O objetivo deste estudo foi verificar qual é o melhor protocolo para extração das clorofilas a, b e total (a + b) a ser aplicado em estudos com a gramínea forrageira Tifton 85 (Cynodon spp.). Os resultados revelaram que os melhores extratores, tomando-se como base os teores de clorofila total (a + b), foram o N,N-dimetilformamida, o dimetilsulfóxido e a acetona 80 por cento (com as equações propostas por ARNON, 1949). A variação temporal dos teores das clorofilas a, b e total ajustaram-se a um modelo hiperbólico comum a todos os solventes, sendo o período de 48 horas considerado suficiente para uma adequada extração.

This study aimed to assess which is the most appropriate protocol for extraction of chlorophylls a, b and total (a + b) to be applied in studies with Tifton 85 (Cynodon spp.) forage grass. Results revealed that, based on total (a + b) chlorophyll contents, the best extractors were N,N-dimethylformamide, dimethylsulfoxide and acetone 80 percent (using the equations proposed by ARNON, 1949). Temporal changes in the concentrations of chlorophyll a, b and total were well described by a hyperbolic model common to all solvents, being the period of 48 hours considered sufficient for an appropriate extraction.

Comparação de métodos diretos de extração e quantificação dos teores de clorofilas em folhas do capim-Tifton 85

This study aimed to assess which is the most appropriate protocol for extraction of chlorophylls a, b and total (a + b) to be applied in studies with Tifton 85 (Cynodon spp.) forage grass. Results revealed that, based on total (a + b) chlorophyll contents, the best extractors were N,N-dimethylformamide, dimethylsulfoxide and acetone 80% (using the equations proposed by ARNON, 1949). Temporal changes in the concentrations of chlorophyll a, b and total were well described by a hyperbolic model common to all solvents, being the period of 48 hours considered sufficient for an appropriate extraction.

O objetivo deste estudo foi verificar qual é o melhor protocolo para extração das clorofilas a, b e total (a + b) a ser aplicado em estudos com a gramínea forrageira Tifton 85 (Cynodon spp.). Os resultados revelaram que os melhores extratores, tomando-se como base os teores de clorofila total (a + b), foram o N,N-dimetilformamida, o dimetilsulfóxido e a acetona 80% (com as equações propostas por ARNON, 1949). A variação temporal dos teores das clorofilas a, b e total ajustaram-se a um modelo hiperbólico comum a todos os solventes, sendo o período de 48 horas considerado suficiente para uma adequada extração.

Comparação de métodos diretos de extração e quantificação dos teores de clorofilas em folhas do capim-Tifton 85

This study aimed to assess which is the most appropriate protocol for extraction of chlorophylls a, b and total (a + b) to be applied in studies with Tifton 85 (Cynodon spp.) forage grass. Results revealed that, based on total (a + b) chlorophyll contents, the best extractors were N,N-dimethylformamide, dimethylsulfoxide and acetone 80% (using the equations proposed by ARNON, 1949). Temporal changes in the concentrations of chlorophyll a, b and total were well described by a hyperbolic model common to all solvents, being the period of 48 hours considered sufficient for an appropriate extraction.

O objetivo deste estudo foi verificar qual é o melhor protocolo para extração das clorofilas a, b e total (a + b) a ser aplicado em estudos com a gramínea forrageira Tifton 85 (Cynodon spp.). Os resultados revelaram que os melhores extratores, tomando-se como base os teores de clorofila total (a + b), foram o N,N-dimetilformamida, o dimetilsulfóxido e a acetona 80% (com as equações propostas por ARNON, 1949). A variação temporal dos teores das clorofilas a, b e total ajustaram-se a um modelo hiperbólico comum a todos os solventes, sendo o período de 48 horas considerado suficiente para uma adequada extração.